The present invention relates to an electrical connector, and especially to a ball grid array (BGA) socket which can effectively resist stress occurred due to different thermal expansion between insulative housing of the BGA socket and a printed circuit board to which the socket is mounted.
U.S. Pat. Nos. 5,593,322; 5,702,255; and 5,716,222 each disclose an electrical connector which comprises a housing and a plurality of contacts. The contacts of the electrical connector are soldered to contact pads of a circuit board by solder balls. The solder balls disposed at the ends of the contacts melt as they are heated and solidify upon cooling for connecting the contact pads and the contacts. During this process, the housing and the circuit board expand and contract, and a relative movement occurs therebetween because the housing and the circuit board each have a different coefficient of thermal expansion (CTE). Thus, a stress exists between the contacts, the solder balls and the contact pads, and the biggest stress exists between the elements distant from a center of the housing. The stress fully acts on the contacts such that the contacts, especially the contacts distant from the center of the housing, may become inadvertently separated from the contact pads on the circuit board thereby disrupting signal transmission. Hence, an improved electrical connector is required to overcome the disadvantages of the prior art.